Downhole pump assembly

ABSTRACT

The invention pertains to oil production pumping equipment in particular to submersible downhole pumps with rod drives to simultaneously and separately lift reservoir fluids to the surface from two reservoirs of a single well. The downhole pump assembly comprises a drive, upper and lower oil-well sucker-rod pumps each connected with its own rod string. In addition to this the unit is equipped with the body, crossbar and joint hollow rod string the latter being attached to the upper part of the crossbar to the bottom of which the rod strings of the upper and lower oil-well sucker-rod pumps are fixed, moreover, the rod string of the upper oil-well sucker-rod pump being made hollow and interconnected with the hollow plunger of the upper oil-well sucker-rod pump and the channel in the crossbar with the joint hollow rod string, and the rod string of the lower oil-well sucker-rod pump is installed between the cylinder of the upper oil-well sucker-rod pump and the downhole pump assembly body, moreover, the upper oil-well sucker-rod pump being offset from the longitudinal downhole pump assembly body axis. Coaxiality of the lower oil-well sucker-rod pump is achieved through the use of the rod crossover shoe, S-shaped rod and non-central pipe sub. The lower plunger pump rod has a shaped cross-section. As a result a standard pumping unit and two oil-well sucker-rod pumps are used and both enhanced reliability of the downhole pump assembly and increased overhaul life of its operation are achieved.

FIELD OF THE INVENTION

The invention pertains to oil production pumping equipment. More specifically it relates to submersible downhole pumps used for extraction of formation fluids from deep wells operating in the conditions of simultaneous stage development.

BACKGROUND OF THE INVENTION

In view of technical benefits and results achieved the invention is most close to a downhole pump assembly used for simultaneous stage development from two formations. It includes a conventional pumping unit, a tubing string, an oil-well sucker-rod pump, a packer, a liner, an auxiliary conventional pumping unit and short tubing string installed at the depth above the upper formation, and a parallel anchor mounted on both tubing strings and above the upper formation, the short tubing string being equipped with another oil-well sucker-rod pump (RU 49895 U1, Oct. 12, 2005). The known equipment is to contain two conventional pumping units, two rod drives, and also two tubing strings, and an anchor. Running operations of two tubing strings entail great labor consumption, processing complexity and losses of time. Prior to any operations in the well, at least, one conventional pumping unit at the surface is to be dissembled, while afterwards it should be reassembled. Moreover the use of two pumping units, two tubing strings, two rod drives, and an anchor doubles financial expenses.

The objective of the invention is to use a standard drive of the pump assembly and two standard oil-well sucker-rod pumps.

The technical effect achieved includes enhanced operation reliability of the downhole pump assembly and increased overhaul period.

SUMMARY OF THE INVENTION

The stated objective is realized and the technical effect is achieved due to the fact that the downhole pump assembly comprises a rod drive, tubing string, upper and lower oil-well sucker-rod pumps each connected with its own rod strings, the downhole pump assembly is equipped with the body, crossbar and joint hollow rod string the latter being attached to the upper part of the crossbar to the bottom of which the rod strings of the upper and lower oil-well sucker-rod pumps are fixed, moreover, the rod string of the upper oil-well sucker-rod pump being made hollow and interconnected with the hollow plunger of the upper oil-well sucker-rod pump and the channel in the crossbar with the joint hollow rod string, and the rod string of the lower oil-well sucker-rod pump is installed between the cylinder of the upper oil-well sucker-rod pump and the downhole pump assembly body, moreover, the upper oil-well sucker-rod pump being offset from the longitudinal downhole pump assembly body axis.

The downhole pump assembly allows operations using only one conventional pumping unit, one tubing string and one rod string with standard oil-well plunger pumps making it possible to choose sizes for every oil-well. The above advantages of the proposed downhole pump assembly allow enhanced operation reliability and increased overhaul period, as well as enable to operate in two or three reservoirs if the well serves as a tubing string.

The rod string of the lower or upper oil-well sucker-rod pumps can consist of one rod.

The axes of the lower oil-well sucker-rod pump and the downhole pump assembly can match, wherein, the rod string of the lower oil-well sucker-rod pump between the crossbar and the lower oil-well sucker-rod pump is equipped with a non-central rod crossover shoe or the rod string of the lower plunger pump is sigmoid bended.

The cross-section of the lower oil-well sucker-rod pump rod connected to the crossbar can be different, for instance, flat, oval, moon-shaped, etc. and the rod position relative to the crossbar is fixed.

The lower oil-well sucker-rod pump is displaced relative to the downhole pump assembly body axis to the opposite side from the upper oil-well sucker-rod pump, wherein, the downhole pump assembly body is connected with the lower oil-well sucker-rod pump by means of a non-central pipe sub.

The centralizers can be placed on the rods.

The pumping unit allows operations using only one conventional pumping unit, one tubing string and one rod string with standard oil-well plunger pumps making it possible to choose sizes for every oil-well. The above advantages of the proposed downhole pump assembly allow enhanced operation reliability and increased overhaul period, as well as enable to operate in two or three formations if the well serves as a tubing string.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal section of the upper part of the downhole pump assembly;

FIG. 2 is a longitudinal section of the lower part of the downhole pump assembly and an optional connection of the lower pump to the upper part through the rod crossover shoe for FIG. 1;

FIG. 3 is a longitudinal section of the lower part of the downhole pump assembly and an optional connection of the lower pump to the upper part through the sigmoid bended rod for FIG. 1;

FIG. 4 is a longitudinal section of the lower part of the downhole pump assembly and an optional connection of the lower pump to the upper part through the pipe sub for FIG. 1;

FIG. 5 is a cross-section of the downhole pump assembly through the upper pump with an optional moon-shaped rod section for FIG. 1;

DESCRIPTION OF THE BEST EMBODIMENT

The innovative downhole pump assembly consists of a body 1, an upper oil-well sucker-rod pump 2 containing a pump chamber 3 in a cylinder 4 with a suction valve 5 and a hollow plunger 6 with an discharge valve 7 in its lower part. The plunger 6 is connected with a hollow rod string 8 through a crossbar 9 with a joint hollow rod string 10. The axis of the upper oil-well sucker-rod pump 2 is biased from the axis of the downhole pump assembly body 1. In the crossbar 9 there is a channel 11 which connects the chamber of the plunger 6 with the chamber of the joint hollow rod string 10 (FIG. 1). Moreover, the crossbar 9 is connected with an upper end of the rod string 12 of a lower oil-well sucker-rod pump 13 (FIG. 2) the lower end of which, in turn, is connected with a made hollow plunger 14 of the lower oil-well sucker-rod pump 13. The rod string 12 is in the moon-shaped chamber formed by the outside surface of the upper oil-well sucker-rod pump 2 and the inner surface of the body 1 where it can reciprocate. A plunger 14 is in a cylinder 15 and its lower end is equipped with a discharge valve 16. In the cylinder 15 there is a suction valve 17 contained in a pump chamber 18. The pump chamber 3 of the upper oil-well sucker-rod pump 2 is connected with an annulus 19 through an inlet port 20 and a channel 21. The pump chamber 18 of the lower oil-well sucker-rod pump 13 is connected with an annulus 22 through an inlet channel 23 (FIG. 2). There is an upper formation 24 and a lower formation 25 in the well. A packer 26 separating the well annuluses 19 and 22 between the formations 24 and 25 is mounted on the body 1. When the distance between the upper and lower oil-well sucker-rod pumps 2 and 13 is short and the lower oil-well sucker-rod pump 13 is located in alignment with the downhole pump assembly body a non-central rod crossover shoe 27 is possible to be installed on the rod string 12 under the upper oil-well sucker-rod pump 2. Instead of the rod crossover shoe 27 to connect the lower oil-well sucker-rod pump (FIG. 3) one can use a sigmoid bended rod which is in the offsetting plane of the upper and lower axis of the oil-well sucker-rod pumps. As an option (FIG. 4) one can also use a non-central pipe sub 28 to connect the lower oil-well sucker-rod pump 13 to the body 1.

When the distance between the upper and lower oil-well sucker-rod pumps 2 and 13 is long there is no need to use the rod crossover shoe 27 or the pipe sub 28 owing to rod flexibility. The upper rod of the rod string 12 which is connected to the crossbar 9 has a shaped profile as, for instance, moon- or trough-shaped, to match profiles of the chamber formed by the outside surface of the upper oil-well sucker-rod pump 2 and the inside surface of the downhole pump assembly body 1 (FIG. 5). The inner section diameter of the moon-shaped rod can match the outside diameter of the upper oil-well sucker-rod pump 2 while the outside section diameter of the moon-shaped rod can match the inside diameter of the body 1 to diminish a fray through probability.

As an alternative, it is proposed to lock the position of the upper rod and then fix it in the crossbar 9 due to the availability of the milled polarizing slots on the upper rod end and in the clamping hole of the crossbar 9 in which a wedge key 29 is mounted and also to the availability of a thread 30 on the upper rod end on which a washer 31, a fastening nut 32 and a retaining nut 33 are screwed to fix the rod in the crossbar 9. Besides, fixation can be performed not by wedge key 29 alone it is also possible to use splines or polyhedrons.

In any of above mentioned options there exist a possibility to mount centralizers (not shown on the drawings) on the rods 8, 10, and 12.

The operation of the downhole pump assembly used for simultaneous stage development of two reservoirs is as follows.

When suction of the pumped out fluid starts the joint hollow rod string 10 moves upward carrying along the plunger 6 of the upper plunger downhole pump 2 and the plunger 14 of the lower oil-well sucker-rod pump 13. Underpressure is built in the pump chamber 3 of the upper oil-well sucker-rod pump 2 and in the pump chamber 18 of the lower oil-well sucker-rod pump 13. With opening of the valves 5 and 17 the fluid leaves both the annulus 19 to enter the pump chamber 3 of the upper oil-well sucker-rod pump 2 and the annulus 22 to enter the pump chamber 18 of the lower plunger oil-well sucker-rod pump 13 since on lowering the downhole pump assembly into the well the packer 26 was brought into an operation state and separated the annulus into two sections 19 and 22, respectfully. After the plungers 6 and 14 reach their top positions and the pump chambers 3 and 18 are filled the joint hollow rod string 10 starts its downward movement. The valves 5 and 17 close while the compressed fluid pressure in the pump chambers 3 and 18 opens the valves 7 and 16 and there occurs a fluid overflow from the pump chamber 3 into the plunger chamber 6 and further on along the joint hollow rod string 10 into the wellhead and from the pump chamber 18 into the plunger chamber 14 and further into the body 1 and then along the tubing string (not shown on the drawing) into the wellhead. When the plungers 6 and 14 are in their bottom positions recycling of the pumps and the downhole pump assembly takes place.

INDUSTRIAL APPLICABILITY

The present invention can find its application in oil producing and some other industries for the recovery of various fluids from wells. 

1. A downhole pump assembly comprises a rod drive, tubing string, upper and lower oil-well sucker-rod pumps each connected with its own rod strings, characterized in that the downhole pump assembly is equipped with the body, crossbar and joint hollow rod string the latter being attached to the upper part of the crossbar to the bottom of which the rod strings of the upper and lower oil-well sucker-rod pumps are fixed, moreover, the rod string of the upper oil-well sucker-rod pump being made hollow and interconnected with the hollow plunger of the upper oil-well sucker-rod pump and the channel in the crossbar with the joint hollow rod string, and the rod string of the lower oil-well sucker-rod pump is installed between the cylinder of the upper oil-well sucker-rod pump and the downhole pump assembly body, moreover, the upper oil-well sucker-rod pump being offset from the longitudinal downhole pump assembly body axis.
 2. A downhole pump assembly according to claim 1, characterized in that the rod string of the lower oil-well sucker-rod pump includes a rod.
 3. A downhole pump assembly according to claim 1, characterized in that the axes of the lower oil-well sucker-rod pump and the downhole pump assembly match.
 4. A downhole pump assembly according to claim 1, characterized in that the rod string of the lower oil-well sucker-rod pump between the crossbar and the lower oil-well sucker-rod pump is equipped with a non-central rod crossover shoe.
 5. A downhole pump assembly according to claim 1, characterized in that the rod string of the lower plunger pump is sigmoid bended.
 6. A downhole pump assembly according to claim 1, characterized in that the lower oil-well sucker-rod pump is displaced relative to the downhole pump assembly body axis to the opposite side from the upper oil-well sucker-rod pump.
 7. A downhole pump assembly according to claim 1, characterized in that the cross-section of the lower oil-well sucker-rod pump rod connected to the crossbar can be different, for instance, flat, oval, moon-shaped, etc. and the rod position relative to the crossbar is fixed.
 8. A downhole pump assembly according to claim 6, characterized in that the downhole pump assembly body is connected with the lower oil-well sucker-rod pump by means of a non-central pipe sub.
 9. A downhole pump assembly according to claim 1, characterized in that the rod string of the upper oil-well sucker-rod pump includes a rod.
 10. A downhole pump assembly according to claim 1, characterized in that there are centralizers on the rods. 